Bhangu JS, et al. - A total of 198 subjects were analyzed to investigate the effectiveness of calcium excretion (CE) and calcium/creatinine clearance ratio (CCCR) in the differential diagnosis of familial hypocalciuric hypercalcemia (FHH) and primary hyperparathyroidism. They noted 24 candidates with low CE whereas 35 patients had a CCCR signifying FHH, though they reported normal or increased CE in 8 cases with FHH. They observed no statistical differences between both methods as sensitivity/specificity were 42.9%/89.9% for CE and 64.3%/79.9% for CCCR. While it may help to narrow down potential FHH patients, either CE nor CCCR could differentiate between PHPT and FHH.